Archive for the 'Trilobites' Category

As I mentioned previously, the antarctic is home to a startling, and poorly surveyed, preponderance of marine life. Now, the British Antarctic Survey has released some excellent photographs of some of these animals. Here are the arthropod highlights (click the photos to embiggen):

Serolid sp. – Wait, yesterday didn’t I say that trilobites are extinct? Well, that is still true. This animal is actually an isopod crustacean, related to terrestrial pill bugs. The flattened body shape of this animal is an adaptation that makes it easier to burrow into sediment.

Antarcturus sp. – Despite the apparent morphological disparity, this is also a member of the isopod order. This animal is a member of the Antarcturidae family. Unlike Serolids, which are bottom-dwelling scavengers, these isopods live on the branches of coral and sponges. They reach their long frontal appendages out in the water column to catch planktonic prey.

These two isopods nicely demonstrate the tremendous amount of morphological diversity that similar animals can evolve in order to best suit their lifestyle. Furthermore, Serolid sp. is a great example of convergent evolution between isopods and trilobites. These two arthropod groups are unrelated, yet species within them have evolved a similar body shape in order to best suit their shared bottom-dwelling lifestyles.

The always hilarious satire periodical, The Onion, has put up a list of the top 10 news articles of the last 4.5 billion years. According to the list, a trilobite extolling on how great it is to be alive during the Cambrian, is the top story in Earth’s history.

The final paragraph is actually quite poetic:

The trilobite then settled down in his murky lagoon, where for the third straight night he would rest soundly while thoughts of someday becoming a brine shrimp, or perhaps even a crustacean—each of which, he knew, would be just a small part of the beautiful upward arc of life, forever changing, forever moving toward balance and harmony—danced in his tiny, insignificant head.

One minor nerdy nitpick, however. Trilobites did not evolve into crustaceans or brine shrimp (which are crustaceans themselves). They were a distinct sister group to the other arthropod sub-phyla. The trilobite lineage is completely extinct; no descendants of these arthropods exist today.